From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754747Ab3KLKln (ORCPT ); Tue, 12 Nov 2013 05:41:43 -0500 Received: from merlin.infradead.org ([205.233.59.134]:55390 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754495Ab3KLKlk (ORCPT ); Tue, 12 Nov 2013 05:41:40 -0500 Date: Tue, 12 Nov 2013 11:41:29 +0100 From: Peter Zijlstra To: Vincent Guittot Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, pjt@google.com, Morten.Rasmussen@arm.com, cmetcalf@tilera.com, tony.luck@intel.com, alex.shi@intel.com, preeti@linux.vnet.ibm.com, linaro-kernel@lists.linaro.org, rjw@sisk.pl, paulmck@linux.vnet.ibm.com, corbet@lwn.net, tglx@linutronix.de, len.brown@intel.com, arjan@linux.intel.com, amit.kucheria@linaro.org, l.majewski@samsung.com Subject: Re: [RFC][PATCH v5 07/14] sched: get CPU's activity statistic Message-ID: <20131112104129.GH4971@laptop.programming.kicks-ass.net> References: <1382097147-30088-1-git-send-email-vincent.guittot@linaro.org> <1382097147-30088-7-git-send-email-vincent.guittot@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1382097147-30088-7-git-send-email-vincent.guittot@linaro.org> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 18, 2013 at 01:52:20PM +0200, Vincent Guittot wrote: > +static int get_cpu_activity(int cpu) > +{ > + struct rq *rq = cpu_rq(cpu); > + u32 sum = rq->avg.runnable_avg_sum; > + u32 period = rq->avg.runnable_avg_period; > + > + sum = min(sum, period); > + > + if (sum == period) { > + u32 overload = rq->nr_running > 1 ? 1 : 0; > + return available_of(cpu) + overload; > + } > + > + return (sum * available_of(cpu)) / period; I'm thinking this has a fair potential to overflow our u32, no? > +}